The present invention relates to safety belt systems employed in automobiles and the like for restraining passengers in their seats during emergency conditions and, more particularly, to safety belt restraint devices employed for restraining a single safety belt and employing a reel from which the safety belt is protracted and retracted.
The use of safety belts for occupant restraint in vehicles has been known for many years. In an effort to secure the benefits of such systems, there has been a constant effort in the industry to improve the systems in order to make them better in operation while, at the same time, of minimal interference to the occupant so as to promote their increased use.
Many such safety belt systems in present used employ a spring-wound reel at one end of the safety belt around which the safety belt is wound for protraction and retraction. Such systems offer relatively unconfined freedom of movement for the occupant during normal conditions. In an emergency condition, the reel is locked by an appropiate mechanism to prevent protraction of the belt and thereby restrain the occupant for the duration of the emergency. The primary locking of the reel is often accomplished by an inertia responsive device such that the occupant is restrained during periods of excessive acceleration and deceleration, as well as upon a striking force against the vehicle from the side.
In studying such systems, it has been found that upon the locking of the reel itself, a certain amount of protraction of the safety belt can still occur depending on the manner in which the belt is wound about the reel and its relative compactness. That is, the belt may slide along itself, compacting the layers on the reel, for a given amount of time. In co-pending application Ser. No. 227,275 filed Jan. 28, 1981, by co-inventor Avraham Ziv herein and entitled SAFETY BELT WEBBING EMERGENCY LOCKING APPARATUS, an improvement to such devices was shown for preventing such continued protraction following lockup of the reel. In the apparatus of that invention, a clamping wedge is disposed in front of the reel, having the seat belt pass therethrough. A second inertia responsive device is connected to activate the clamping wedge so as to directly clamp the belt upon a second level of inertia being encountered greater than that necessary to primarily lockup the reel.
Heavier individuals tend to compact the layers of seat belt upon the reel and achieve protraction after lockup to a greater degree than lighter individuals. This weight or force responsive protraction is independent of the degree of inertia involved. Wherefore, it is the object of the present invention to provide an alternate embodiment to the invention of the aforementioned application which alternate embodiment is responsive protraction forces on the seat belt webbing itself following primary lockup rather than inertia forces on the vehicle.